The invention relates to heat exchangers, especially for motor vehicles, and more particularly to a heat exchanger of the type comprising a fluid chamber equipped with a peripheral foot, as well as a collector plate equipped with a peripheral edge delimiting a peripheral groove which features a bottom and is at least partially able to accommodate the peripheral foot, with a compressible sealing gasket being interposed.
A heat exchanger of this type further comprises means for immobilizing the peripheral foot relative to the collector plate, at the same time compressing the sealing gasket. This immobilization is achieved, for example, by a crimping operation.
In a heat exchanger of this type, the sealing gasket has to ensure perfect leaktightness in order to avoid any problem of leakage and of corrosion.
A gasket made of an elastomer material of the rubber type, for example of the EPDM type, is usually used, which is prepared in advance then put in place in the peripheral groove of the collector plate before receiving the peripheral foot of the fluid chamber.
The fitting of such a gasket prepared in advance is a delicate operation since it is necessary for the gasket to be perfectly positioned in the peripheral groove, which is usually U-shaped in profile. However, it may happen that the sealing gasket does not lodge perfectly in the bottom of the peripheral groove, which has the consequence that this gasket is not perfectly compressed after the peripheral foot of the fluid chamber has been put in place. This results in defects in leaktightness which mean that the heat exchanger thus manufactured does not satisfy the checks carried out on leaving the manufacturing line and therefore has to be scrapped.
The object of the invention is especially to surmount the abovementioned drawbacks.
The invention aims, in particular, to obtain a heat exchanger which comprises an improved sealing gasket which is perfectly positioned in the bottom of the peripheral groove and which thus offers perfect leaktightness after the peripheral foot of the fluid chamber has been positioned.
The invention also envisages obtaining a method of manufacturing such a heat exchanger.
To that end the invention proposes a heat exchanger of the type defined in the introduction, in which the sealing gasket is formed from a bead of a polymerizable material which is deposited, at a chosen location, on the bottom of the peripheral groove and which is then polymerized before being compressed by the peripheral rim of the collector chamber.
Thus the sealing gasket of the invention is formed in situ on the bottom of the peripheral groove from a bead made of polymerizable material, which is then polymerized in situ.
As this bead is deposited directly onto the bottom of the peripheral groove, and at a chosen location on it, the invention makes it possible to deposit the sealing gasket under controlled conditions as regards not only the location where the bead is deposited but also the particular shape of the gasket.
The gasket preferably extends over a height, from the bottom of the peripheral groove, which is greater than its width. It has been observed that, under these conditions, an optimal seal was obtained. The height of the gasket is to be considered from the bottom of the peripheral groove, that is to say in the direction of compression of the gasket.
The gasket may be single and result from the depositing of one bead layer or else be double and result from the depositing of two superimposed bead layers.
In this latter case, the double gasket can be applied either in a single pass or in two successive passes.
The peripheral groove is usually delimited, furthermore, by two sidewalls which extend from the bottom.
According to an important characteristic, the invention also provides for the bead to be deposited on the bottom and at a distance from each of the said sidewalls.
In that way, the gasket is bonded solely to the bottom of the groove and is spaced away from the two sidewalls, without being able to bond to the latter.
This results in the gasket therefore being able to be deformed in an appropriate way during the compression resulting from the peripheral foot being put in place. This deformation takes place optimally with no risk of detaching or tearing of the gasket.
In the invention, the polymerizable material is advantageously based on silicone.
As regards another aspect, the invention relates to a method of manufacturing a heat exchanger of the type defined above, which comprises the following operations:
a) providing a collector plate equipped with a peripheral edge delimiting a peripheral groove featuring a bottom;
b) depositing a bead of a polymerizable material, at a chosen location, on the bottom of the peripheral groove in order to form a sealing gasket;
c) polymerizing the said bead in order to form a polymerized gasket; and
d) compressing the polymerized gasket by a peripheral foot of a fluid chamber.
Operation b) is advantageously carried out by a nozzle which is moved above the bottom of the peripheral groove. This movement can be made either manually, or preferably automatically, for example by the use of a template, under controlled conditions.
In operation b), the bead may be deposited either in a single layer in order to form a single gasket, or in two layers in order to form a double gasket.
In all cases, the gasket is preferably applied in a single pass of the nozzle.
According to another characteristic of the invention, in operation b), the bead is deposited on the bottom of the peripheral groove, and at a distance from two sidewalls which are connected to the bottom.
In operation c), polymerization of the gasket is advantageously carried out by application of heat, in order to accelerate the polymerization.
According to yet another characteristic of the invention, the method comprises a subsequent operation e) consisting in immobilizing the peripheral foot of the fluid chamber in the peripheral edge of the collector plate.